Early pregnancy loss is an important concern and the subject of current and planned studies of reproductive hazards in the work place. Its determination requires the measurement of urinary human chorionic gonadotropin (hCG). We have very recently discovered that many of the measurements of hCG may be highly inaccurate because of the presence of peptide bond nicks in the urinary hCG which makes the hormone invisible to the antibodies currently used for its measurement. Furthermore, preliminary gel blotting studies of both serum and urine of pregnant women indicate significant concentrations of nicked hCG may be present in the circulation. These findings require immediate verification to avoid the necessity of re-exploring the current and proposed studies with new measuring systems. The objectives of this proposal are (1) to develop standards for the nicked forms of hCG in order to evaluate current antibody libraries to select potential measurement systems; (2) to measure the expression of all forms of hCG present in existent early pregnancy loss urine specimens now being cognizant of the possible presence of substantial concentrations of nicked hormone; (3) to collect parallel serum and urine specimens throughout pregnancy and compare the concentrations of the forms of hCG present in both serum and urine (4) to produce monoclonal antibodies to nicked forms of hCG to improve its measurement by development of a specific IRMA to a unique epitope expressed by nicked forms of hCG.